Tropical fish dying

This is a discussion on Tropical fish dying within the Tropical Fish Diseases forums, part of the Freshwater Fish and Aquariums category; -->
Hi.
One of my fish die roughly every 10 days
I have a 360 litre tank with nitrate, nitrite and ammonia at 0.0 and ...

Hi.
One of my fish die roughly every 10 days
I have a 360 litre tank with nitrate, nitrite and ammonia at 0.0 and PH 8.3 temp 26 (in green band) - this shows as normal for all of them
I have two filter systems - orignal jewel system and a EHMI system.
I have tried varoius frequencies of carrying out water changes about 80 litres every week or fornight.
I change the filters as recommended
I do have plants so weekely add plant food
I feed them once a day 6 times a week
Why is this happening?
Also another question, I recently when I saw a few ill, tried adding salt. Is this ok?

specifically what kind of fish do you have?? and how long has the tank been set up?

I have rosy barbs, tiger barbs, yellow barbs , (not at home so can do list next time i am home) lots of barbs, two cat fish and few small sanils.
Tank been around for a round 1 year and I change the white filter fornightly, carbon one 8 weeks and others every few months. I clean the filters in the dirty water from the tank (pumped into a bucket). I only shake and rinse the media in the container it stays in

I looked up in my book and see that the barbs you have like acidic water. and you have more alkaline water. They like the water to be 6.5-7 ph. you have at least one whole unit higher than they like. This could cause some stress. Not saying it is for sure the problem but it is something you could keep in mind.